Communications using virtual local area networks (VLANs) have been performed to separate a single transmission cable into different networks. For example, a network constructed in a train consists of a trunk transmission line extending over all vehicles and one or more branch transmission lines divided for apparatuses or each type of apparatus in a plurality of vehicles. In order to reduce cost and avoid complexity in cable wiring, in some cases, a vehicle network with a single physical transmission cable in which a trunk network is separated from one or more branch networks is constructed.
For example, Patent Literature 1 uses a VLAN technique to limit the broadcast frame transmission range (transferred range). Patent Literature 2 applies VLANs thereby to use fewer LAN cables.